By Michael Eliasohn
When it comes to building human powered vehicles, Bill "Yoda" Irvine likes to keep them simple. They also are unique, and although a home-builder, he's probably built more than some supposed manufacturers.

The Phoenix, Ariz. resident, during this writer's visit in early October 2009, guessed he had built at least 75 HPVs, and more since, and that he had built his first one about four years earlier. What he builds, he sells. And despite the number, he said, "It is a hobby." Most of the bikes he has built were recumbents.